As is generally known, ozone or chemicals such as chlorine are used to carry out sterilization and disinfection of water supply and sewerage, sterilization, deodorization and decoloration of industrial water, bleaching of pulp, or sterilization of medical instrumentation.
In a conventional sterilizing apparatus, a retention tank and a stirring device such as a spray pump has been required in order to dissolve ozone or chemicals in the water to be treated, and thus it has not been possible to immediately cope with change in water quality or quantity. On the other hand, ultraviolet rays have a function of sterilization, disinfection and decoloration of water supply and sewerage, decomposition of persistent organic substances, deodorization and decoloration of industrial water, and bleaching of pulp, and the effect is exerted even when the irradiation time of the ultraviolet rays is several seconds or less. Thus, in an ultraviolet water treatment apparatus configured to carry out ultraviolet irradiation, when a high-intensity high-power ultraviolet lamp is used as the ultraviolet light source, the ultraviolet lamp is arranged perpendicular to a cylindrical water-passage barrel in some cases (“Maintenance Manual for Ultraviolet Treatment Facilities in Application to Water other than Surface Water” Foundation for Water Supply Technical Center, July, 2009).
FIGS. 7A and 7B show an example of an ultraviolet water treatment apparatus using a conventional high-intensity high-power ultraviolet lamp, where FIG. 7A shows a front view of the ultraviolet water treatment apparatus, and FIG. 7B shows a cross-sectional view taken along the line X-X in FIG. 7A.
The ultraviolet water treatment apparatus 1 comprises a cylindrical water-passage barrel 3 through which water to be treated flows, a lamp housing 4 joined crisscross to the cylindrical water-passage barrel 3 at a central part of the barrel 3 and having a diameter identical with the cylindrical water-passage barrel 3. In the lamp housing 4, six ultraviolet irradiation tubes 7, each having a lamp protective tube 5 made of quartz glass and a ultraviolet lamp 6 disposed in the lamp protective tube 5, are arranged at an equal interval. Each of both ends of each ultraviolet irradiation tube 7 is water-sealed on a lamp housing rid 8 by means of a watertight O-ring (not shown) and an O-ring retainer 9. Further, a cleaning device including a cleaning plate drive shaft 10, a drive screw (not shown), a drive motor 11, a cleaning plate 12 and a lamp protective tube wiper 13 is set in the lamp housing 4. In the ultraviolet water treatment apparatus 1 having such a configuration, ultraviolet lamps of the same specification are used. It should be noted that a reference symbol 14 in FIG. 7A denotes treated water.
However, since an amount of dirty substances contained in the water to be treated is large or small depending on the water treatment facilities, there has been a problem that when the type of water or the quantity of water changes, sufficient ultraviolet treatment cannot be carried out by the conventional ultraviolet water treatment apparatus.